WALL RELAXATION IN GROWING STEMS - COMPARISON OF 4 SPECIES AND ASSESSMENT OF MEASUREMENT TECHNIQUES
WALL RELAXATION IN GROWING STEMS - COMPARISON OF 4 SPECIES AND ASSESSMENT OF MEASUREMENT TECHNIQUES
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DOI：
10.1007/bf00391104
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发表时间：
1987-06-01
期刊：
影响因子：
4.3
通讯作者：
COSGROVE, DJ
中科院分区：
文献类型：
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作者：
COSGROVE, DJ
本研究的目的是发展改进的方法来测量生长组织的体内应力松弛，并比较四种不同物种的茎的松弛。当生长组织的水吸收被阻止时，体内应力松弛发生，因为持续的壁松弛降低了壁应力和细胞膨压。利用该程序，可以测量生长的屈服阈值（Y）、超过屈服阈值的膨压（P-Y）和生理壁伸展性（v φ）。三种松弛技术被证明是有用的：“turgor-relaxation”，“平衡压力”和“压力块”。在膨压松弛法中，水从生长的组织中被截留，并且膨压的减少直接用压力探针测量。该技术给出了P和Y的绝对值，但需要切除组织。在平衡压力技术中，切除的生长区域被密封在压力室中，随后的水势降低被测量为使木质部汁液返回切割表面所需的施加压力。这种方法很简单，但只测量（P-Y），而不是P和Y的单独值。在压力阻断技术中，生长中的组织被密封在压力室中，生长被连续监测，并且刚好足够的压力被施加到室以阻断生长。该方法给出了高分辨率的松弛动力学，并且不需要组织切除，而只需测量（P-Y）。这三种方法在豌豆生长茎上得到了相似的结果，黄瓜（Cucumis sativus L.），大豆（Glycine max（L.）梅尔）和西葫芦（Zucchini）（西葫芦L.）幼苗（P-Y）的平均值在1.4和2.7巴之间，取决于物种。屈服阈值平均在1.3巴至3.0巴之间。与其他方法相比，压力块松弛更快，并表现出动态变化的壁屈服性能。两个压力室的方法也被用来测量内部的水势梯度（木质部和表皮之间），驱动水的吸收生长。对于这四个物种来说，它很小，在0.3和0.6巴之间，因此基本上不会限制生长。
This study was carried out to develp improved methods for measuring in-vivo stress relaxation of growing tissues and to compare relaxation in the stems of four different species. When water uptake by growing tissue is prevented, in-vivo stress relaxation occurs because continued wall loosening reduces wall stress and cell turgor pressure. With this procedure one may measure the yield threshold for growth (Y), the turgor pressure in excess of the yield threshold (P-Y), and the physiological wall extensibility (.vphi.). Three relaxation techniques proved useful: "turgor-relaxation", "balance-pressure" and "pressure-block". In the turgor-relaxation method, water is withheld from growing tissue and the reduction in turgor is measured directly with the pressure probe. This technique gives absolute values for P and Y, but requires tissue excision. In the balance-pressure technique, the excised growing region is sealed in a pressure chamber, and the subsequent reduction in water potential is measured as the applied pressure needed to return xylem sap to the cut surface. This method is simple, but only measures (P-Y), not the individual values of P and Y. In the pressure-block technique, the growing tissue is sealed into a pressure chamber, growth is monitored continuously, and just sufficient pressure is applied to the chamber to block growth. The method gives high-resolution kinetics of relaxation and does not require tissue excision, but only measures (P-Y). The three methods gave similar results when applied to the growing stems of pea (Pisum sativum L.), cucumber (Cucumis sativus L.), soybean (Glycine max (L.) Merr.) and zucchini (Curcubita pepo L.) seedlings. Values for (P-Y) averaged between 1.4 and 2.7 bar, depending on species. Yield thresholds averaged between 1.3 and 3.0 bar. Compared with the other methods, relaxation by pressure-block was faster and exhibited dynamic changes in wall-yielding properties. The two pressure-chamber methods were also used to measure the internal water-potential gradient (between the xylem and the epidermis) which drives water uptake for growth. For the four species it was small, between 0.3 and 0.6 bar, and so did not limit growth substantially.